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Pleasure for Some, Torment for Others

For the eyes, reading is a fine motor skill, jumping in quick jerks from one word to the next in just fractions of a second. Depending on one’s reading proficiency, the eyes rest on individual letters of a word for 200 to 450 milliseconds and even skip some words altogether. Experts speak of saccades and fixations when characterizing the fine-tuned eye movements controlled by the eye muscles. Tracking these rapid eye movements is a standard procedure in cognitive psychology. Experts in this field study the factors that control our perception. They examine how we gain and process knowledge and how emotions influence our actions. Analyzing eye movements offers scientists numerous answers to a wide variety of questions.

It is a bit like at the eye doctor’s when laboratory supervisor Petra Schienmann positions the head correctly for eye tracking – the measurement of eye movements. Here in the EyeLab at the University of Potsdam stands the Eye-Link® 1000 – a rather bulky device with highly sensitive technology. The integrated high-speed camera focuses the right eye and takes up to 1000 pictures per second. During the measurement, the head rests on a frame that is equipped with chin and forehead pads. The eyes look onto a monitor from which participants are instructed to read example sentences. “Afterwards we can say where you looked for how long,” Schienmann explains.

Anja Sperlich is a PhD student at the University of Potsdam and examines the eye movements of primary school children during reading. Duration, frequency, and position of eye movements tell the researcher how children process texts and how their reading competence develops. She also wants to find out what factors influence learning to read.

Anja Sperlich is doing her PhD together with 11 other young academics at the University of Potsdam within the Research Training Group “Intrapersonal Developmental Risk Factors in Childhood and Adolescents: A Longitudinal Perspective”, which was launched in 2011 and is funded by the Deutsche Forschungsgemeinschaft (DFG). The empirical data is collected as part of the large-scale PIER (Potsdamer Intrapersonale Entwicklungsrisiken) Study. About 3100 children and adolescents from about 220 schools in Brandenburg have taken part in this study.

Anja Sperlich began her study in 2012. “We contacted about 300 families and eventually got 141 children to participate in the elaborate laboratory testing,” she tells us. We invited 1st, 2nd, and 3rd graders to the University’s EyeLab, where they were asked to read short sentences on a monitor, such as “Dinosaurs lived many million years ago. The biggest dinosaur was bigger than a house.” Then the children chose which of the two pictures matched what they had read before. A sun appeared on the monitor for correct answers and a dark rain cloud for incorrect ones. The scientist tested the same children a year later and observed how reading competence had changed. “Children often remembered how many suns and rain clouds they had collected the year before,” Schienmann says and smiles.

Sperlich uses the moving-window paradigm. Sentences are manipulated in such a way that subjects can only read the text in a small variable-width window of 7-29 letters. The window moves across the sentence at the speed of the participants’ eye movements when reading. Letters outside the window are altered and masked by Xs. This method enables the researchers to determine the perceptual span, the size of visual field within which we can take in information for processing. “Our visual field is limited,” the researcher explains. The experts call the area of sharpest central vision the fovea centralis.

The fovea centralis is surrounded by the parafovea, where visual acuity is lower but still allows for taking in textual information. While the gaze remains on a word, experienced readers already start preprocessing the next one. “We experimentally manipulate the extent to which readers can preview by showing only a pre-defined window of useful information,” Sperlich describes the procedure. “If we expand the window up to a size that does not hinder the normal flow of reading, we know how many letters can be processed with one gaze.”

After the reading test, Sperlich opens a file showing the previously read sentences with a fine red line on them – the visual track. In most cases a little knot lies on each word. This is where the eye rested for a few milliseconds before moving on to the next word with a saccade. Longer and more difficult words show several knots. Short function words like ‘in’ or ‘of’ have no fixation points. “Experienced readers skip almost every third word,” Sperlich says. The red line sometimes shows backward movements – regressions – if individual words or passages were reread. On a large data sheet, the psychologist inputs details about each recorded fixation – duration, length of the following saccade, the within-sentence and the within-word position, etc. The analyses are based on about 165,000 fixations.

Sperlich links the data of the eye-tracking experiment to results of other reading tests usually used to diagnose dyslexia. Children took these tests at school, supervised by young scientists of the PIER study. Statistical analyses show whether the measurement of eye movements produced similar results as the other reading tests. “Reading problems in children can be easily detected with the usual tests”, Sperlich underlines, but tracking the eye movements allows a direct observation of the reading process. “There are already many programs that can help pupils with dyslexia,” says Sperlich. After all, 5% of the population is affected. However, these programs have to be further optimized. “Only after we have understood the sequence of processes involved in reading, we can begin to improve these programs to fit the needs of poor readers and help them more efficiently.” Her examinations provide the basis for it.

Initial results have confirmed the prevalent hypothesis: “Children who have just started reading make longer and more frequent fixations and shorter saccades than experienced readers.” While first graders fixate on each word several times, a third grader often needs only one fixation per word. The perceptual span increases the more experienced a reader is. “After about sixth grade, it is fully developed, at least in the English language. Our experiments will show whether this also holds true also for German,” says Sperlich. This parameter can also vary depending on the difficulty of the text. “When I read a demanding text, my cognitive capacities are more exhausted, and the perceptual span decreases,” Sperlich explains.

However, the scientist was surprised that the differences in reading performance increase within a grade level as the children get older, an interpretation which other research also suggests. “When children are exposed to books before going to school, it promotes their interest in reading. How often they read seems to increasingly affect their reading performance,” Sperlich clarifies. The more often a child reads, the faster certain partial processes of reading are automatized. “This releases cognitive capacities that can be used for a deeper reading comprehension,” the scientist explains. In further examinations, Sperlich will analyze the connections between automatization, text processing, and size of perceptual span at different points of measurement. The initial data already suggests, however, that if children do not find an approach to literature in their leisure time quite early, school can hardly make up for the difference between passionate and reluctant readers. Performance drifts further apart and consolidates. Whether children are bookworms or ‘hate’ reading – “the foundation for a successful development of the reading skill seems to be laid at preschool age,” Sperlich explains. Teachers and parents should observe and promote children’s interest in reading at a young age.


Visitors to the exhibition “Forschungsfenster” can see the principle of the “Moving-Window Paradigm” at the newly opened exhibition floor of science at the Potsdam Bildungsforum. In addition to the EyeLab’s research work, interactive presentations introduce current research topics at academic institutions of Brandenburg and Potsdam. The exhibition is open from 10 am to 6 pm on weekdays and 10 am to 2 pm on Saturdays.


Anja Sperlich studied psychology at the University of Potsdam and has been doing her PhD since 2011 under the supervision of Dr. Jochen Laubrock and Prof. Ulrich Schiefele within the DFG Research Training Group “Intrapersonal Developmental Risk Factors in Childhood and Adolescents: A Longitudinal Perspective”.


Universität Potsdam,
Department Psychologie
Karl-Liebknecht-Straße 24-25
14476 Potsdam

Text: Heike Hartmann, Online-Editing: Julia Schwaibold, Translation: Susanne Voigt